Although numerous studies have been undertaken to examine sites/mechanisms of action of various nephrotoxicants, specific identification of subcellular sites/mechanisms are lacking for most substances. Biochemical studies which have demonstrated the importance of renal metabolism in the activation of certain toxic chemicals have not revealed the mechanism by which these activated chemicals exert their toxicity nor have they demonstrated unequivocally the subcellular site on which they act. The proposed studies are designed to examine the hypothesis that disruption of membrane function may underlie the actions of nephrotoxicants. Direct studies of this nature are possible because of the relatively recent technical developments for the preparation of separate populations of basolateral and brush border membrane vesicles, each of which retain their intrinsic transport characteristics. These membranes can be used to examine specific transport properties under rigidly controlled in vitro experiments. Hence, specific functions associated with each membrane can be examined in a preparation devoid of other cellular influences. In these studies, the relative sensitivity of basolateral versus brush border membrane vesicle transport to a variety of xenobiotics will be tested. The effects of nephrotoxicants will be examined on both membrane types in an effort to reveal which membrane type shows the greatest sensitivity as judged by dose-response and time course studies. These studies might suggest whether nephrotoxicants act on the urinary or blood side of the cell. The binding or transport by membrane vesicles of certain nephrotoxicants also will be examined with both membrane vesicle preparations. Finally, since an important physiological role has been established for adrenergic receptor mechanisms in basolateral membranes, the interaction of nephrotoxicants with this receptor process will be studied. Disruption of this mechanism might underlie the initiation of nephrotoxicity. The nephrotoxicants to be studied are mercuric chloride, potassium dichromate, citrinin and hexachloro-1,3-butadiene. The membrane vesicles will be prepared from rat renal tissue by Percoll gradient centrifugation.